Carell and Timothée at "Beautiful Boy" premiere

ROUGH CUT.

NO REPORTER NARRATION.

Known for comedies like "Anchorman" and "The 40-Year-Old Virgin" as well as the darker "Foxcatcher", Carell plays real-life American writer David Sheff in the movie, which is based on the memoirs of Sheff and his son Nic.

The tough and at times tear-jerking film sees Carell's character struggle to come to terms with the problem, as a teenage Nic, a keen reader and writer with a promising future in college, gets addicted to drugs including crystal meth, goes to rehab, but repeatedly relapses.

"I identified with the fear of a father, of really any parent," Carell, who has two children, said at the movie's UK premiere at the BFI London Film Festival on Saturday (October 13).

"I think it's relevant, it's very timely, it's an epidemic ... I hope that people realise ... addiction ... has all sorts of stigmas applied to it which it shouldn't have." Chalamet, who was nominated for an Oscar this year for "Call Me by Your Name", plays Nic, vividly portraying the character as he moves between highs and aggressive lows.

"If you're talking about the using stages ... not in an ironic way there's many a video on YouTube and just you go to rehab and ask people about their experiences," he said, when talking about preparing for his performance.

"There's a comfort in thinking that drug addicts or addiction can't affect your family or yourself when the reality is that it's a very human disease, it doesn't discriminate." The 22-year-old was greeted by screaming fans upon arrival in London's Leicester Square, with some even giving him gifts such as books and socks on the red carpet.